Seamless alginate capsules having a variety of desirable characteristics are described in WO 03/084516. Seamless alginate capsules having an alginate in the shell membrane possessing a relatively high amount of G blocks provide strong capsules when compared to capsules having an alginate in the shell membrane possessing a relatively high amount of M blocks. However, seamless alginate capsules having a high G alginate content in the shell membrane have not been found to have fast disintegration in gastric environment, and, generally, gels made of high-M alginates generally have a poor mechanical strength compared to gels made of high-G alginates. Furthermore, increasing the concentration of an alginate having a high M content in the shell membrane would be expected to unacceptably increase process viscosity and create very difficult processing conditions, while decreasing the molecular weight of such an alginate would be expected to undesirably result in further weakening the (already very weak) capsules even at high concentrations.
It is desired, therefore, to develop a seamless alginate capsule that has the desired capsule strength and disintegration profile in gastric environment while solving the processing difficulties associated with capsule manufacture. The inventors tested numerous alginates varying M content, molecular weight and concentration, among other variables, and unexpectedly found a suitable process that provides capsules having unexpected strength and disintegration in the gastrointestinal environment.